Proton NMR imaging may have important clinical potential for the evaluation of the myocardium. It has already been shown to provide tomographic and high resolution images of the heart without ionizing radiation or potentially harmful contrast agents. In addition it has the potential for characterization of myocardium using the relaxation parameters T1 and T2. Preliminary studies described in this application suggest that analysis of T1 and T2 will be useful for staging the ischemic process. The long term objective of the applicants is to develop and evaluate the ability of NMR to characterize the myocardium. The objective of this proposal is define the utility of NMR to characterize ischemic myocardium. The specific aims are: 1) to define the intracelluar biochemical energetics of ischemia and hypoxia and realte these changes to changes in T1 and T2 values, 2) to define the time course of T1 and T2 changes resulting from myocardial ischemia with and without reperfusion, 3) to evaluate the utility in patients of gated proton NMR imaging with dipyriodamole infusion to detect coronary artery disease, 4) to evaluate the ability of NMR imaging in patients with myocardial infarction with and without reperfusion to characterize the state of the myocardium and quantify myocardial damage, and 5) to evaluate the ability of proton NMR imaging to measure myocardial wall motion and ejection fraction. The usefulness of this research will be the development of a non-invasive method to characterize the state of the myocardium inpatients with ischemic heart disease. It is anticipated that this method will be able to distinguish between irreversibly damaged myocardium and potentially salvagable myocardium. It is hoped that this method will permit quantitation of the severity and extent of ischemic damage and the effects of interventions.